This invention relates to cardiac surgery and more particularly to an apparatus and method of use of such apparatus in cardiac bypass surgery recovery with the aim of minimising dangers of such surgery particularly in the recovery phase.
Cardiac surgery, particularly open heart surgery has and remains to be associated with significant risk to the patient, nevertheless there is a trend of incremental developments in surgery techniques and apparatus which tends to reduce risks in the operation.
It has long been recognised, for example by research into the effects of nitrogen narcosis (the bends), gas embolisms and the like manifesting in gas bubble entrainment within the body""s vascular system can have adverse effects, such as subsequently impaired brain function or neurocognitive deficits.
It is implicit that in most cases open heart surgery carries with it at least a risk of gas bubble (normally air) and particulate emboli entrainment in the vascular system as a result of the interior of the heart, or the blood vessels associated with the heart becoming punctured, disconnected and open to atmosphere.
In the past, toward completion of a bypass open heart operation, as the surgical repairs are completed, the operating staff undertake various steps in order to xe2x80x9cflushxe2x80x9d or xe2x80x9cbleedxe2x80x9d the bypassed region in an endeavour to remove all potential emboli, for example air bubbles, particles and the like from the heart and the associated bypassed vascular system. Such steps have typically included xe2x80x9cbleedingxe2x80x9d the region via a puncture in the aorta coupled with careful filling of the heart with cardioplegia or blood, aspirating the heart at various positions for example by syringe punctures, coupled with physical manipulation of the heart, for example by squeezing, tilting, suction venting and the like.
Whilst such steps tend to remove most of entrained emboli from the heart and the associated bypassed region, in view of the xe2x80x9ccavitiedxe2x80x9d structure of the heart and associated blood vessels, coupled with the buoyancy of gas bubbles and their tendency to xe2x80x9cadherexe2x80x9d to adjacent surfaces, it has been found inevitable that gas bubbles remain in the bypassed region. Tests have shown that despite the most diligent attention to emboli removal, these techniques are not completely effective; at re-instatement of normal circulation by removal of the aortic clamp, gas bubble numbers in the region of 1000 to 5000 at closure of the operation are commonly detected being expelled by the recovered heart and its associated blood vessel system. These bubbles are then transported to the body organs.
It is an object of this invention to provide an apparatus and/or method of use of such apparatus which at least comes some way in addressing the problems abovenoted, or at least provide the public with a useful choice.
Other objects of this invention will become apparent from the following description.
According to one aspect of this invention there is provided a fluid control device adapted for communication with a fluid supply, said flow control device including a pressure control means adapted to control a fluctuating fluid pressure in said device wherein said pressure control means is normally biased toward a closed position for maintaining a predetermined level of upstream backpressure, but is openable under the bias under predetermined additional pressure to release fluid from said fluid control device, said pressure control means providing a bias which is proportional to an extent of opening of said pressure control device and the predetermined additional pressure.
According to a further aspect of this invention there is provided a fluid control device adapted for connection in controlled communication with a bypassed heart region, and a heart fluid supply for said bypassed heart region, said fluid control device including a variable resistance pressure control means adapted to control heart fluid flow from, and/or fluctuating pressure in, said bypassed heart region, said pressure control means including an opening in communication with said bypassed heart region normally biased toward a closed position for maintaining a predetermined level of upstream backpressure, but variably openable against the bias under predetermined additional heart fluid pressure in said bypassed heart region to release through said opening heart fluid from said bypassed region, said pressure control means providing a bias which is proportional to a cross-sectional area of the opening in said pressure control means and the predetermined additional heart fluid pressure in said bypassed heart region.
According to a still further aspect of this invention there is provided a method of improving the removal of potential emboli from a bypassed heart region prior to removal of said region from bypass including the steps of connecting a fluid control device in communication with an output portion of said bypassed heart region, said fluid control device having a variable resistance pressure control device in communication with said bypassed heart region capable of releasing heart fluid from said fluid control device over a predetermined pressure, filling said bypassed heart region with heart fluid and allowing said heart to pump said heart fluid whilst in a bypassed condition, and whilst maintaining an inflow of heart fluid to said bypassed heart region.
According to a still further aspect of this invention there is provided a system for reducing potential emboli from a bypassed heart region prior to removal of said region from bypass, a fluid control device adapted for connection in controlled communication with a bypassed heart region and a heart fluid supply for said bypassed heart region, said fluid control device including a variable resistance pressure control means adapted to control a heart fluid flow from and/or pressure in said bypassed heart region, said pressure control means normally biased towards a closed position, but openable against the bias under predetermined heart fluid pressure in said bypassed heart region to release heart fluid from said bypassed heart region, said pressure control means providing a bias which is proportional to cross-sectional area of an opening in said pressure control means and heart fluid pressure in said bypassed heart region.
According to a still further aspect of this invention there is provided a fluid control device including a conduit assembly connectable for controlled communication with a bypassed heart region and a venous line of a body vascular system including a variable resistance pressure control means variably biased to a normally closed position for maintaining a predetermined level of upstream backpressure and openable under additional predetermined aortic heart fluid pressure to at least partially control fluctuating heart fluid pressure in the bypassed heart region, said fluid control device connectable with a fluid reservoir and/or oxygenation device for circulation of heart fluid between said bypassed heart region and said fluid reservoir and/or oxygenation device whilst said bypassed heart region is at least partially bypassed, said pressure control means adapted to control the fluctuating heart fluid pressure in said at least partially bypassed heart region during heart filling and subsequent heart pumping; where said heart moves heart fluid in said bypassed portions of said heart during a recovery period, prior to completion of removal of said bypassed heart region from the bypassed condition.
Other aspects of this invention which should be considered in all its novel aspects will become apparent from the following description. Modifications are envisaged and may be incorporated without departing from the scope or spirit of the invention.